Flexographic printing plate

Abstract

To provide a flexographic printing plate capable of securing uniformity of thickness of a printed film up to a periphery of a printing region.SOLUTION: A flexographic printing plate P includes plane-view shapes of a plurality of projections formed on a dot pattern. A central region 2A of a projection for printing 2 is different in terms of the dot pattern from peripheral regions 2B and 2C located on a periphery of the central region 2A.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a printing plate used for flexographic printing, and more particularly, to a flexographic printing plate capable of performing uniform printing up to the periphery.

Background Art

[0002] Flexographic printing is generally performed by a printing machine as shown in FIG. 14. This printing machine includes a cylindrical plate cylinder 51 on which a flexographic printing plate P1 is mounted, an anilox roll 52 for attaching ink to the flexographic printing plate P1, an ink supply device 53 for supplying ink to the surface of the anilox roll 52, a doctor 54 for scraping off excess ink on the surface of the anilox roll 52, and a printing stage 55 on which a printing object Q to be printed is placed.

[0003] The flexographic printing by the printing machine is performed as follows. That is, the flexographic printing plate P1 is mounted on the circumferential side surface of the plate cylinder 51, and while rotating the plate cylinder 51, the ink supplied from the ink supply device 53 is attached to the printing area of the flexographic printing plate P1 via the anilox roll 52, and the attached ink is transferred to a printing object Q such as a glass substrate placed on the printing stage 55, thereby performing printing (formation of a printing film). At this time, the printing stage 55 is slid in synchronization with the rotation of the plate cylinder 51.

[0004] Here, the flexographic printing plate P1 generally includes a flat base 11 and a printing convex portion 12 formed at the central portion of the surface of the base 11, as shown in a plan view in FIG. 15A and a cross-sectional view taken along the line M-M of FIG. 15A in FIG. 15B. The printing convex portion 12 is the printing area, and the portion of the base 11 around the printing convex portion 12 is not involved in printing. Also, as shown in an enlarged cross-sectional view of the main part of FIG. 15B in FIG. 15C, a plurality of protrusions 13 are distributed on the top surface of the printing convex portion 12 with grooves 14 therebetween, and ink is held in the grooves 14. Furthermore, the flexographic printing plate P1 is flexible so that it can be attached to the peripheral surface of the plate cylinder 51 (see Figure 14).

[0005] However, in the flexographic printing method described above, the printing protrusions 12 of the flexographic printing plate P1 come into contact with the anilox roll 52 and the substrate Q. Due to the pressure exerted during this contact, the ink held on the printing protrusions 12 accumulates in the peripheral region (for example, peripheral region 12B) of the printing protrusions 12. As a result, the thickness of the printed film formed by the flexographic printing method can be thicker in the peripheral region surrounding the center than in the center, a phenomenon known as the "marginal effect."

[0006] Therefore, various proposals have been made to suppress the occurrence of marginal phenomena. For example, Patent Documents 1 and 2 propose a flexographic printing plate in which the distribution density of protrusions 13 formed on the printing protrusions 12 is set higher in the peripheral region 12B than in the central region 12A of the printing protrusions 12. In other words, by increasing the distribution density of protrusions 13 in the peripheral region 12B of the printing protrusions 12, the size of the grooves 14 formed between the protrusions 13 is reduced, the amount of ink held in the grooves 14 is reduced, and the thickness of the peripheral part of the printed film is suppressed from becoming thicker. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Patent No. 3376908 [Patent Document 2] Japanese Patent Publication No. 2002-293049 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] On the other hand, flexographic printing requires various performance characteristics in addition to suppressing the occurrence of marginal phenomena. For example, with recent technological advancements, a high level of uniformity is required, and it is now necessary to ensure uniformity of the printed film thickness even to the periphery of the printed area.

[0009] This invention has been made in view of these circumstances, and aims to provide a flexographic printing plate that can ensure uniformity of the printing film thickness up to the periphery of the printing area. [Means for solving the problem]

[0010] However, in view of these circumstances, the inventors conducted extensive research and found that by forming the planar shape of the multiple protrusions formed on the top surface into a halftone pattern, and by making the halftone pattern different between the central region of the printing protrusions and the peripheral region located around the periphery of the central region, the linearity of the arrangement of multiple protrusions formed at the edge of the peripheral region can be increased, thereby suppressing positional variations at the edge of the printed film (alignment film) to accommodate the narrow bezels of liquid crystal panels, and thus completing the present invention.

[0011] In other words, the present invention has the following aspects. [1] A flexographic printing plate having a plurality of printing protrusions formed on its top surface, wherein the plurality of protrusions have a planar shape formed in a halftone pattern, and the halftone pattern differs between the central region of the printing protrusion and the peripheral region located at the periphery of the central region. [2] The flexographic printing plate according to [1], wherein the halftone pattern in the peripheral region is a collection of halftone dots arranged in rows, and the angle T between a virtual line R connecting the centers of adjacent halftone dots arranged in rows and the printing direction S is set to 0°±10° or 45°±10°. [3] The flexographic printing plate according to [1] or [2], wherein the halftone pattern in the central region is a collection of halftone dots arranged in rows, and the angle T between a virtual line R connecting the centers of adjacent halftone dots arranged in rows and the printing direction S is set to 11° to 34° or 56° to 79°. [4] The peripheral region has a printing direction portion along the printing direction and a perpendicular direction portion along a direction perpendicular to the printing direction, and a ratio (W / X) of the width W of the printing direction portion of the peripheral region to the width X of the printing convex portion is set such that 0 < W / X < 0.05. The flexographic printing plate according to any one of [1] to [3]. [5] In the halftone dot pattern in the peripheral region, the pitch of adjacent halftone dots arranged in a columnar shape is set to 20 μm to 300 μm. The flexographic printing plate according to any one of [1] to [4]. [6] In the halftone dot pattern in the peripheral region, the distances of the halftone dots arranged in six surrounding directions adjacent to each other are set to be equal. The flexographic printing plate according to any one of [1] to [5]. [7] In the peripheral region, the halftone dot pattern is different between the printing direction portion and the perpendicular direction portion, and the distribution density of the halftone dots in the printing direction portion is set higher than the distribution density of the halftone dots in the perpendicular direction portion. The flexographic printing plate according to any one of [1] to [6]. [Effect of the Invention]

[0012] According to the flexographic printing plate of the present invention, a plurality of protrusions are formed in a halftone dot pattern in a plan view shape, and the halftone dot pattern is different between the central region of the printing convex portion and the peripheral region located at the periphery of the central region. Therefore, the linearity of the protrusion array formed at the end of the peripheral region can be enhanced. Therefore, by performing printing using this flexographic printing plate, the uniformity of the thickness of the printing film can be ensured up to the periphery of the printing region, and it becomes possible to use up to a portion that could not be used conventionally due to the non-uniform thickness of the printing film. Thus, the printing film can be efficiently produced. [Brief Description of the Drawings]

[0013] [Figure 1] FIG. 1 is a plan view schematically showing a flexographic printing plate according to an embodiment of the present invention. [Figure 2] FIG. 2 is an enlarged view of a main part in the J-J cross section of FIG. 1. [Figure 3] Figure 3 is an enlarged view of the main part at the K-K cross-section of Figure 1. [Figure 4] Figure 4 is an enlarged view of the main part of the peripheral region among the parts surrounded by the dashed line L in Figure 1. [Figure 5] Figure 5 is a diagram for explaining the case where the angle T formed by the virtual line R and the traveling direction S in Figure 4 is 0°. [Figure 6] Figure 6 is an enlarged view of the main part of the central region among the parts surrounded by the dashed line L in Figure 1. [Figure 7] Figure 7 is a diagram for explaining the angle T formed by the virtual line R and the traveling direction S in Figure 6. [Figure 8] Figure 8A is a diagram for explaining the linearity of the protrusion arrangement at the end of the peripheral region when the angle T formed by the virtual line R and the traveling direction S is 0°. Figure 8B is a diagram for explaining the linearity of the protrusion arrangement at the end of the peripheral region when the angle T is -5°. Figure 8C is a diagram for explaining the linearity of the protrusion arrangement at the end of the peripheral region when the angle T is -10°. [Figure 9] Figure 9A is a diagram for explaining the linearity of the protrusion arrangement at the end of the peripheral region when the angle T formed by the virtual line R and the traveling direction S is 45°. Figure 9B is a diagram for explaining the linearity of the protrusion arrangement at the end of the peripheral region when the angle T is 40°. Figure 9C is a diagram for explaining the linearity of the protrusion arrangement at the end of the peripheral region when the angle T is 35°. [Figure 10] Figure 10A is a diagram obtained by partially enlarging and photographing the flexographic printing plate of the embodiment of the present invention. Figure 10B is a diagram obtained by partially enlarging and photographing the flexographic printing plate of the comparative example of the present invention. [Figure 11] Figure 11A is a diagram for explaining a dot pattern formed by dots arranged in a columnar pattern in both the vertical and horizontal directions. Figure 11B is a diagram for explaining a dot pattern set such that the distances between the dots arranged in the six surrounding directions adjacent to each other are equal. [Figure 12] Figure 12 is a diagram for explaining the difference in the distribution density of dots between the printing direction part and the right-angle direction part in the dot pattern of the peripheral region. [Figure 13]FIG. 13 is a diagram for explaining the depth of the grooves between a plurality of protrusions formed in the dot pattern arrangement of FIG. 12. [Figure 14] FIG. 14 is an explanatory diagram schematically showing a printing machine using a flexographic printing plate. [Figure 15] FIG. 15A is a plan view schematically showing a conventional flexographic printing plate. FIG. 15B is an enlarged view of a main part in the M-M cross section of FIG. 15A. FIG. 15C is an enlarged cross-sectional view of the main part of FIG. 15B.

Embodiments for Carrying Out the Invention

[0014] Hereinafter, the present invention will be described in more detail based on embodiments of the present invention, but the present invention is not limited to the following embodiments. In the present invention, when expressed as "Y to Z" (Y and Z are arbitrary numbers), unless otherwise specified, it includes the meaning of "Y or more and Z or less" and also the meaning of "preferably larger than Y" or "preferably smaller than Z". Also, when expressed as "Y or more" (Y is an arbitrary number) or "Z or less" (Z is an arbitrary number), it also includes the meaning of "preferably larger than Y" or "preferably less than Z".

[0015] <<First Embodiment>> FIG. 1 is a plan view schematically showing an embodiment of a flexographic printing plate of the present invention, FIG. 2 is an enlarged view of a main part of the J-J cross section of FIG. 1, and FIG. 3 is an enlarged view of a main part of the K-K cross section of FIG. 1. The flexographic printing plate P of this embodiment includes a flat base 1 rectangular in plan view and a printing convex portion 2 rectangular in plan view formed at the central portion of the surface of the base 1. On the top surface of the printing convex portion 2, a plurality of frustum-shaped minute protrusions 3 are distributed with gaps (grooves 4) therebetween, and ink is held in these grooves 4. The base 1, the printing convex portion 2, and the protrusions 3 are integrally formed. And in this embodiment, the direction of the arrow S along the long side of the printing convex portion 2 rectangular in plan view is set as the printing direction (progressing direction).

[0016] The flexographic printing plate P is used for flexographic printing and is flexible enough to be attached to the peripheral surface of the plate cylinder 51 of a printing press (see Figure 14). Examples of materials for forming the flexographic printing plate P include resin and rubber. Examples of methods for forming the flexographic printing plate P include mold molding, and when using a photosensitive resin as the forming material, it is preferable to form it by photolithography.

[0017] The dimensions of the frustoconical projection 3 can be set, for example, to a diameter of 20 to 70 μm for the top surface, a diameter of 185 to 300% of the diameter of the top surface for the bottom surface, and a depth D from the top surface to the bottom of the groove 4 within a range of 5 to 25 μm (see Figure 2). Furthermore, the distribution density of the protrusions 3 can be set to a range of 100 to 1300, for example, when expressed as the number of protrusions 3 per inch (25.4 mm).

[0018] The printing protrusion 2 is divided into two main regions (parts). Specifically, depending on the distribution of the protrusions 3, the printing protrusion 2 is divided into a central region 2A and peripheral regions 2B and 2C located around the periphery of the central region 2A. The halftone dot pattern (hereinafter sometimes referred to as "halftone dot pattern") that is recognized as the planar shape of the protrusion 3 differs between the central region 2A and the peripheral regions 2B and 2C. Here, the halftone dots recognized as the plan view shape of the projection 3 refer to the top surface of the projection 3, not the bottom surface. This is to align with the usual calculation of the aperture ratio based on the area of ​​the top surface of the projection 3.

[0019] <Peripheral regions 2B, 2C> First, the peripheral regions 2B and 2C of the printing protrusion 2 will be described. Figure 4 illustrates the halftone dot pattern in a plan view of the multiple protrusions 3 formed in the peripheral regions 2B and 2C within the area enclosed by the dashed line L in Figure 1. In this embodiment, the halftone dot patterns in peripheral regions 2B and 2C are the same, with rows of halftone dots 3a collectively forming a halftone dot pattern. The angle T between the imaginary line R connecting the centers 3b of adjacent rows of halftone dots 3a and the printing direction S is set to 0°. Note that in Figure 4, the halftone pattern of the protrusion 3 formed in the central region 2A is omitted. Also, since the imaginary line R and the direction of travel S are parallel and do not intersect each other, the angle T is not shown.

[0020] In the aforementioned halftone pattern, the imaginary lines connecting the centers 3b of adjacent halftone dots 3a arranged in a row include not only the imaginary line R shown in Figure 4, but also the imaginary line r1 connecting the centers 3b of adjacent halftone dots 3a in the vertical direction (up and down direction of the paper), as shown in Figure 5. Additionally, there is a virtual line r2 connecting the centers 3b of adjacent halftone dots 3a in a diagonal direction (upward sloping from left to right on the page). However, as shown in Figure 11A, in the aforementioned halftone pattern, the distance between the centers 3b of adjacent halftone dots 3a is longer when the halftone dots are adjacent in the diagonal direction (distance E2) than when the halftone dots are adjacent in the vertical and horizontal direction (distance E1). Therefore, to obtain the virtual line R, the halftone dots 3a selected are those adjacent in the vertical and horizontal direction, and those adjacent in the diagonal direction are not selected, as shown in Figure 5 (although not shown, the same applies to halftone dots 3a adjacent in the upward-sloping direction of the paper). In this invention, when multiple imaginary lines can be drawn in this manner, the imaginary line whose angle with the direction of travel is 0° or more and less than 90° is defined as the imaginary line in this invention. Therefore, as shown in Figure 5, in the halftone pattern, the angle t between the virtual line r1 and the direction of travel S is 90°, so it is not used. Also, as mentioned above, the virtual line r2 is not used because it increases the distance between adjacent halftone dots 3a.

[0021] Thus, when the angle T between the virtual line R of the halftone pattern in peripheral regions 2B and 2C and the printing direction S is 0°, the linearity of the arrangement of each protrusion 3 formed at the outermost edge of the printing protrusion 2 is enhanced (to make the arrangement easier to see, lines (virtual lines F) tangent to the outside of the protrusion 3 (halftone dot 3a) are drawn; the same applies hereafter), as shown in the area enclosed by the dashed line in Figure 8A. Note that the angle T is not indicated in Figure 8A. Similarly, when the angle T is set to 0°±10° or 45°±10°, the linearity of the arrangement of each projection 3 formed at the outermost end is enhanced (see Figures 8B and 8C).

[0022] In other words, when the angle T is -5°, as shown in the dashed line in Figure 8B, the linearity of the arrangement of each projection 3 formed at the very end (dummy line F) is slightly disrupted (there are parts at the end where no projection 3 is formed), but it still has sufficient linearity. Furthermore, when the angle T is -10°, as shown in the dashed line in Figure 8C, the linearity of the arrangement of each projection 3 formed at the outermost edge (dummy line F) becomes even more disrupted (there are parts where no projections 3 are formed at the edge), but it still maintains an acceptable level of linearity. Figures 8B and 8C illustrate patterns shifted by 5° or 10° in the negative direction when angle T is 0°. However, even in patterns shifted by 5° or 10° in the positive direction, the arrangement of each projection 3 formed at the outermost edge exhibits similar linearity.

[0023] On the other hand, as shown in the area enclosed by the dashed line in Figure 9A, the linearity of the arrangement of each projection 3 formed at the outermost end (virtual line F) is also enhanced when the angle T is 45°. And, similar to the case where the angle T is 0°, the linearity is similarly enhanced in the vicinity of the angle T being 45°.

[0024] In other words, when the angle T is 40°, as shown in the dashed line in Figure 9B, the linearity of the arrangement of each projection 3 formed at the outermost edge (dummy line F) is slightly disrupted (there are parts at the end edges where no projections 3 are formed), but it still maintains sufficient linearity. Also, when the angle T is 35°, as shown in the portion surrounded by the dashed line in FIG. 9C, although the linearity of the arrangement (virtual line F) of each protrusion 3 formed at the outermost end is further disrupted (there is a portion where no protrusion 3 is formed at the end side), it has an acceptable linearity. Note that FIGS. 9B and 9C illustrate patterns shifted by 5° or 10° in the -(minus) direction when the angle T is 45°. However, even for patterns shifted by 5° or 10° in the +(plus) direction, the arrangement of each protrusion 3 formed at the outermost end has a similar linearity.

[0025] And as shown in FIG. 1, the peripheral regions 2B and 2C have a printing direction portion 2B along the printing direction and a right-angle direction portion 2C along the direction perpendicular to the printing direction. However, the ratio (W / X) of the width W of the printing direction portion of the peripheral region to the width X of the printing convex portion 2 is preferably 0 < W / X < 0.05. Also, the width X is preferably 0.1 mm or more and 1 mm or less. That is, it is preferably smaller to minimize the influence on the active area. On the other hand, in order to obtain the effect of improving linearity, it is necessary to arrange a certain number of halftone dots in the peripheral region in an arrangement different from the halftone dot pattern in the central region. The width W of the printing direction portion 2B is the sum (W1 + W2) of the widths of the left and right edges (W1, W2) with respect to the printing direction, and the widths W1 and W2 may be the same as or different from each other. If the width W is too small, the area of the peripheral region 2B becomes too small, and it tends to be difficult to form a desired halftone dot pattern. If the width W is too large, the area of the central region 2A becomes too small. For example, when the object to be printed is an array substrate, even if a halftone dot pattern is set to solve the problem of regularly occurring uneven ink thickness, the obtained effect tends to decrease. Thus, when the ratio (W / X) is within the above range, the balance between the complexity of halftone dot pattern design and the obtained effect is excellent.

[0026] Furthermore, in the halftone dot pattern in peripheral regions 2B and 2C, the pitch of adjacent halftone dots 3a arranged in rows is not particularly limited, but is preferably set to 20 μm to 300 μm, and more preferably to 30 μm to 90 μm. In other words, a shorter pitch is advantageous in terms of linearity, but if the pitch is too short, it becomes difficult to secure the volume of the groove 4, and there is a tendency for it to be unable to hold the required amount of ink. However, when the pitch of adjacent halftone dots 3a is set within the aforementioned range, an excellent balance is achieved between linearity and ink holding capacity. As shown in Figures 4, 11A, and 11B, the pitch of adjacent halftone dots 3a represents the distance H at which the distance between halftone dots 3a is shortest. <Central area> Next, the central region 2A of the printing protrusion 2 will be described. Figure 6 illustrates the halftone dot pattern of the protrusion 3 formed in the central region 2A within the area enclosed by the dashed line L in Figure 1. In this embodiment, the angle T between the imaginary line R connecting the centers 3b of adjacent halftone dots 3a arranged in a row and the printing direction S is set to 68°. Note that in Figure 6, the halftone dot pattern of the protrusions 3 formed in peripheral regions 2B and 2C is omitted.

[0027] Figure 7 illustrates the method for selecting the virtual line R used in the present invention when multiple virtual lines can be drawn in the halftone pattern of Figure 6. As described above, when multiple virtual lines can be drawn, the present invention defines a virtual line as one in which the angle T between the virtual line and the direction of travel is 0° or more and less than 90°. For this reason, in the halftone pattern shown in Figure 6, a virtual line R that slopes upward to the left relative to the paper surface is used, rather than a virtual line r1 that slopes upward to the right relative to the paper surface. This is because, as shown in Figure 7, the angle t1 between the virtual line r1 and the direction of travel S is 158° or the angle t2 is -22°. Furthermore, a virtual line r2 is not used because it would increase the distance between adjacent halftone dots 3a.

[0028] The halftone pattern in the central region 2A is not particularly limited, but when an array substrate is used as the substrate, it is preferable that the angle T between the imaginary line R connecting the centers 3b of adjacent halftone dots 3a arranged in a row and the printing direction S is 56° to 79°.

[0029] In other words, around the contact holes formed on the array substrate of a liquid crystal panel, surface tension and fine debris (residue) generated during contact hole formation can repel the ink transferred by flexographic printing, preventing the ink from sufficiently penetrating the contact holes. This can result in uneven film thickness of the alignment layer around the contact holes, causing film thickness inconsistencies. Typically, contact holes formed on an array substrate are arranged regularly in rows. Therefore, when grooves holding ink come into contact with areas around the contact holes where ink repelling occurs, film thickness unevenness becomes noticeable in those areas. If this noticeable film thickness unevenness occurs regularly, the film thickness unevenness becomes even more prominent.

[0030] This problem is addressed because, in the central region 2A, if the angle T between the imaginary line R connecting the centers 3b of adjacent halftone dots 3a arranged in a row and the printing direction S is 56° to 79°, the grooves 4 that hold the ink tend to make less regular contact with the arrangement of contact holes formed on the array substrate, thereby preventing the film thickness unevenness from becoming more noticeable. Furthermore, this method is also suitable when the angle T is between 11° and 34°, as it prevents the film thickness unevenness from becoming more noticeable.

[0031] Thus, in the flexographic printing plate P of the first embodiment, the halftone pattern in the peripheral regions 2B, 2C is set such that the angle T between the imaginary line R connecting the centers 3b of adjacent halftone dots 3a arranged in the row and the printing direction S is set to 0°±10° or 45°±10°. Therefore, the linearity of the arrangement of protrusions 3 formed at the outermost edge of the peripheral region 2B is enhanced, and the amount of ink that can be held in the grooves 4 formed between the protrusions 3 can be made uniform all the way to the periphery of the peripheral region 2B. Furthermore, if the halftone pattern in the central region 2A is set such that the angle T between the imaginary line R connecting the centers 3b of adjacent halftone dots 3a arranged in the row and the printing direction S is set to 11° to 34° or 56° to 79°, then, for example, when an array substrate is used as the substrate, film thickness unevenness can be made less noticeable in most of the printed area. Therefore, by flexographic printing using this flexographic printing plate P, printed films such as alignment films in liquid crystal displays, organic light-emitting films in organic EL displays, and electrode films in electronic devices can be formed to every corner with improved thickness uniformity.

[0032] <<Second Embodiment>> In the second embodiment, the halftone dot pattern of the peripheral regions 2B and 2C in the first embodiment (see Figure 11A) is modified so that the distance between each halftone dot 3a arranged in the six adjacent directions around the periphery is equal, as shown in Figure 11B. In other words, in the first embodiment, as shown in Figure 11A, the distance between the centers 3b of adjacent halftone dots 3a is longer when the distance between adjacent halftone dots 3a in the diagonal direction (distance E2) than when the distance between adjacent halftone dots 3a in the vertical and horizontal direction (distance E1). Therefore, to obtain the virtual line R, halftone dots 3a adjacent in the vertical and horizontal direction are selected, but halftone dots 3a adjacent in the diagonal direction are not selected. On the other hand, in the second embodiment, as shown in Figure 11B, the distances (distance E3) between each of the six adjacent halftone dots 3a arranged in the surrounding directions are made equal, thereby reducing variations in the depth and length of the grooves 4. When the variations in the depth and length of the grooves 4 are reduced, the variations in the amount of ink held in each part are reduced, and the uniformity of the thickness of the printed film can be further improved. Furthermore, if we assume that the distance between adjacent halftone dots 3a arranged in the six surrounding directions is equal, then the same result can be obtained regardless of whether the adjacent halftone dots 3a in the vertical, horizontal, or diagonal directions are connected by the virtual line R. Therefore, the halftone dots 3a for obtaining the virtual line R can be selected in any way, and in Figure 11B, the angle T between the virtual line R and the direction of travel S is set to 55°.

[0033] When adopting a halftone dot pattern for peripheral regions 2B and 2C in which the distances between adjacent halftone dots 3a arranged in the six surrounding directions are equal, the angle T between the virtual line R and the direction of travel S is not particularly limited, but in particular, when the angle T between the selected virtual line R and the direction of travel S is set to one of 0°±10°, 30°±10°, or 60°±10°, there is a tendency for the linearity of the array of protrusions 3 formed at the outermost edge of peripheral region 2B to be further enhanced.

[0034] <<Third Embodiment>> In the third embodiment, the halftone dot pattern of the peripheral regions 2B and 2C in the first embodiment (see Figure 4) is made different in the printing direction portion 2B and the perpendicular direction portion 2C of the peripheral regions 2B and 2C, as shown in Figure 12, and the distribution density of halftone dots 3a in the printing direction portion 2B is set higher than the distribution density of halftone dots 3a in the perpendicular direction portion 2C. As for the distribution density, for example, the distribution density of halftone dots 3a in the printing direction portion 2B is set to a range of 200 to 400 dots / inch, and the distribution density of halftone dots 3a in the perpendicular direction portion 2C is set to a value higher than the distribution density of halftone dots 3a in the printing direction portion 2B, within the range of 400 to 600 dots / inch.

[0035] In this way, by setting the distribution density of the halftone dots 3a in the perpendicular direction portion 2C and the printing direction portion 2B to be different, the ink held in the grooves 4 of the printing protrusion 2 spreads more uniformly on the top surface of the printing protrusion 2 due to the pressure when the printing protrusion 2 comes into contact with the anilox roll 52 of the printing press and the substrate Q. Furthermore, of the peripheral regions 2B and 2C adjacent to the periphery of the central region 2A, the printing direction portion 2B, which is aligned with the printing direction, and the perpendicular direction portion 2C, which is aligned perpendicular to the printing direction, overlap at four corners, and these four corner portions shall be included in the aforementioned perpendicular direction portion 2C.

[0036] In this third embodiment, as shown in Figure 13, the depth D1 from the surface of the protrusion 3 in the printing direction portion 2B and the depth D2 from the surface of the protrusion 3 in the perpendicular direction portion 2C are different, and it is preferable to set the depth to D1 > D2. As for the depths, for example, the depth D1 in the printing direction portion 2B may be set to a value smaller than D1, within the range of 15 to 25 μm, and the depth D2 in the perpendicular direction portion 2C may be set to a value smaller than D1, within the range of 5 to 15 μm. Setting D2 to a smaller value reduces the amount of ink held in the groove 4, which tends to prevent deterioration of the linearity of the printed film edges due to the spread of excess ink during printing.

[0037] [Examples] Figure 10A is a partially enlarged photograph of a flexographic printing plate P in which the halftone pattern in the central region 2A is set to have an angle T of 72°, and the halftone pattern in the peripheral region 2B is set to have an angle T of 45°. For example, when printing an alignment film resin (ink) onto an array substrate, the central region 2A, which occupies most of the surface of the printing protrusions 2 of the flexographic printing plate P, shows less noticeable film thickness unevenness, and the peripheral region 2B enhances the regularity (linearity) of the arrangement of the protrusions at the outermost edge (see the boundary between the peripheral region 2B and the base 1 in Figure 10A). As a result, the amount of ink that can be held in the grooves 4 formed between the protrusions 3 can be made uniform all the way to the periphery of the peripheral region 2B.

[0038] [Comparative Example] Figure 10B shows a partially enlarged image of a flexographic printing plate P1 in which the halftone dot pattern in the central region 2A and the halftone dot pattern in the peripheral region 2B are identical, and in both cases the angle T is set to 72°. Although this design requires only one halftone pattern setting, thus saving time on setup, the arrangement of protrusions at the outermost edge of the peripheral region 2B of the printing protrusion 2 is irregular (lacking linearity) (see the boundary between the peripheral region 2B and the base 1 in Figure 10B), resulting in variations in the amount of ink that can be held in the grooves 4 formed between the protrusions 3 at the periphery of the peripheral region 2B. [Industrial applicability]

[0039] The present invention is useful as a flexographic printing plate that can perform uniform printing even to the periphery. [Explanation of Symbols]

[0040] 2. Printable raised area 2A central area 2B Peripheral area (printing direction portion) 2C Peripheral area (perpendicular part) P Flexographic Printing Plate S Direction of travel

Claims

1. A flexographic printing plate having a printing protrusion with multiple protrusions formed on its top surface, The aforementioned multiple protrusions have a planar shape formed in a halftone pattern. Each of the aforementioned multiple protrusions is frustoconical in shape, The diameter of the top surface of the projection is set in the range of 20 to 70 μm. The diameter of the bottom surface of the projection is set to be in the range of 185 to 300% of the diameter of the top surface of the projection. The depth from the top surface of the projection to the top surface of the printing protrusion is set in the range of 5 to 25 μm. The halftone pattern differs between the central region of the printing protrusion and the peripheral region located at the periphery of the central region. The dot pattern in the central region is a collection of dots arranged in rows, and the angle T between the imaginary line R connecting the centers of adjacent dots arranged in rows and the printing direction S is set to 11° to 34° or 56° to 79°. The halftone dot pattern in the peripheral region is a collection of halftone dots arranged in rows, and the angle T between the imaginary line R connecting the centers of adjacent halftone dots arranged in rows and the printing direction S is set to 0°±10° or 45°±10°. A flexographic printing plate characterized in that, in the halftone dot pattern in the peripheral region, the distance between each halftone dot arranged in the six surrounding directions is set to be equal.

2. The peripheral region has a portion in the printing direction that is aligned with the printing direction and a portion in the perpendicular direction that is perpendicular to the printing direction. The flexographic printing plate according to claim 1, wherein the ratio (W / X) of the width W of the printing direction portion of the peripheral region to the width X of the printing protrusion is set to 0 < W / X < 0.

05.

3. The flexographic printing plate according to claim 1 or 2, wherein the pitch of adjacent halftone dots arranged in a row in the halftone dot pattern in the peripheral region is set to 20 μm to 300 μm.

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